Residential and commercial waste water streams are commonly treated by either on-site (e.g., septic systems) or municipal waste water systems. In both instances, the waste water is subjected to some form of aerobic and/or anaerobic biological treatment, in order to render the constituents of the waste stream safe prior to being discharged into the environment.
The efficacy of the biological treatment processes utilized in these systems are quite sensitive to levels of certain constituents in the waste stream. In particular, with respect to the present invention, significant components of the waste stream include the following:
(1) Fats, Oils and Grease (referred to herein as “F.O.G.”);
(2) Biochemical Oxygen Demand (referred to herein as “B.O.D.”), which is directly related to the levels of undigested food present in the waste stream;
(3) Total Suspended Solids (referred to herein as “T.S.S.”), which includes levels of both food and human waste; and
(4) Fecal Bacteria Count (referred to herein as “FECAL”).
While most residential waste water streams have F.O.G., B.O.D., T.S.S., and FECAL levels which are within acceptable limits, restaurants and other commercial/institutional food service operations (referred to collectively herein as “food service establishments”) often produce waste water streams which far exceed acceptable limits in one or more of these categories.
In particular, food service establishments tend to introduce very high levels of grease and undigested food into the waste water stream via the kitchen sink, into which these materials are flushed from pots, pans, dishes and utensils prior to being washed. For example, in a typical food service establishment, the first step in the dishwashing process is to quickly scrape the largest pieces of uneaten food into a trash can, and then rinse the plates/utensils off using a spray nozzle before placing them in the wash sink or in a mechanical dishwasher. The intended purpose of the initial scraping step is to reduce the amount of large-sized food solids which are flushed down the drain (mostly in an effort to prevent clogging), but in fact manual scraping is grossly inefficient and leaves very large amounts of food/grease on the cookware/servingware and utensils, thus necessitating the preliminary rinse step. Moreover, food service establishment dishwasher personnel are often poorly paid and constantly harried to work faster, with the result that the initial scraping is often cursory at best.
As a result, food service establishment waste water streams are commonly characterized by F.O.G., B.O.D., and T.S.S. levels which far exceed acceptable limits. For example, many food service establishments having on-site waste water treatment systems (usually, a septic tank and drain field) are required by regulation to maintain waste water streams within parameters such as the following:
F.O.G. 40 ppm B.O.D 230 ppm T.S.S. 145 ppm
In fact, because of the problems noted above, the following waste water test results are more typical for a commercial restaurant operation:
F.O.G. 3,000 ppm B.O.D. 21,000 ppm T.S.S. 3,900 ppm
As can be seen, these levels exceed acceptable parameters by up to 100 times, which means that not only is such a restaurant operating well out of regulatory limits for an on-site treatment system, but in fact the drain field and other components of such a system will be rendered inoperable in a comparatively short time, necessitating extremely expensive repairs. This problem is aggravated by the large amount of water which is used to rinse the plates/utensils, which not only increases the water bills for the facility, but can also lead to excessive hydraulic loading of the septic system.
Municipal waste water treatment systems (i.e., sewer systems) also typically require food service establishments to maintain F.O.G., B.O.D., and T.S.S., levels within certain, comparable limits, since high levels of these components will similarly impair the operation of municipal sewage plants and impact their ability to discharge effluent which is within environmentally acceptable limits. As a result, the waste water streams of food service establishments are routinely tested by municipalities to ensure that they are within specified limits, and if the limits are exceeded the establishment may be subjected to fines and/or surcharges to compensate the municipality for the additional costs involved in treating the material.
For these reasons, many restaurant and other food service establishment operators have had to install complicated and expensive systems in an effort to remove food and grease from their waste water streams. For example, many restaurants and other food service establishments have installed very costly waste water grease collection and trap systems. Under ideal operating conditions, many of these systems are capable of removing up to 98% of the grease from the waste water. Unfortunately, proper operation of these systems is, as a rule, highly sensitive to the levels of food and particulate material in the waste stream; in other words, the grease extractor systems are capable of effectively removing grease/oil from the waste water streams, but only if virtually all of the food is scraped off of the plates/utensils before they are rinsed or washed. For the reasons discussed above, however, it is the rare exception that the plates/utensils are scraped completely clean before they are introduced into the water stream, with the result that grease extractors systems installed at food service establishments almost invariably require high levels of maintenance, and are often clogged or otherwise rendered inoperative by high food levels in the waste water. Moreover, even when grease extractor systems are functioning properly, they are very expensive to service and maintain, since special facilities are required for disposal of the collected material and servicing cannot be performed by conventional septic tank pumping companies.
In some extreme instances, restaurants and other food service establishments using on-site waste water treatment systems have been forced to construct much larger treatment systems in order to handle the high F.O.G., B.O.D., and T.S.S. loads produced by their operations. Because of the space limitations common in restaurants and other commercial operations, many of these enlarged waste water systems must be located “off-site” at a remote locations which are capable of accommodating the much larger drain fields. This involves extreme expense, in purchasing the additional real estate, laying piping to the remote site, and installing the additional drain field. Such costs are simply beyond the reach of many food service establishments, especially independent restaurant operations, which are then faced with the prospect of having to close down the business.
Accordingly, there exists a need for an apparatus which can be used to reduce F.O.G., B.O.D., and T.S.S. levels in food service establishment waste water streams to within acceptable levels. Furthermore, there exists a need for such an apparatus which will reduce or eliminate the necessity for any pre-wash rising of plates and utensils, so as to reduce the total amount of water which is used in the washing process. In addition, there exists a need for such an apparatus which is sufficiently effective and convenient to use that it will be employed effectively by food service establishment kitchen personnel. Still further, there exists a need for such an apparatus which is sufficiently inexpensive to be economically available to the majority of food service establishment operations, and which is also reliable and inexpensive to maintain. Still further, there exists a need for such an apparatus which is safe and sufficiently quiet for use in a kitchen facility, which is commonly located adjacent the dining area of the food service establishment.
U.S. Pat. No. 6,434,783 describes such an apparatus. However, the apparatus described therein has certain limitations, including excessive vacuum turbulence in the collection vessel.